<!-- Funktionen, um Content-Div auf gleiche Höhe zu setzen //-->
function numSort(a, b)
{
	return a - b;
}

function equalColumns()
{
	var col1 = document.getElementById("container");
	var col2 = document.getElementById("mainWrapper");
	var col3 = document.getElementById("main");
	
	col1H = col1.offsetHeight;
	col2H = col2.offsetHeight;
	col3H = col3.offsetHeight;

	var divHeights = new Array(col1H, col2H, col3H);
	divHeights.sort(numSort);		// kleinster / mittlerer / großer Wert
	divHeights.reverse();			// Array umkehren
	maxDivHeight = divHeights[0];
	
	// Alle Content-Divs auf die gleiche Höhe setzen
	col1.style.height = maxDivHeight + "px";
	col2.style.height = maxDivHeight + "px";
	col3.style.height = maxDivHeight - 30 + "px";
}
<!-- Ende //-->